Heat Stress Safety: The Science Behind the WBGT Regional Guidelines

October 7, 2019 Monica Devlin Comments

Heat stress is a very real and potentially deadly occurrence that can happen to athletes of any competition level. Since many athletes train and perform in a variety of environmental conditions, Wet Bulb Globe Temperature (WBGT) Regional Guidelines were developed to help improve heat stress safety.

What is WBGT?

First, let's discuss the concept behind Wet Bulb Global Temperature. This is the measurement of heat stress in direct sunlight. This measurement takes the following into account for its calculation:

Humidity
Temperature
Wind Speed
Sun Angle
Cloud cover

It's no secret that different regions of the US experience varying types of weather. This is why there are implemented regional guidelines. An 85-degree day in Ohio can feel much different than an 85-degree day in New Mexico depending on the local climate conditions.

How The Regional Guidelines were Developed

Between 1980 and 2014, a study was conducted that analyzed the relationship between WBGT regional deviations and 61 American football players who had a fatal exertional heatstroke (EHS). For this specific study, the measurements used to indicate fatal levels of heatstroke included wet bulb, globe, and dry temperature.

The weighted average integrates several environmental factors as well as human heat balance, directly related to gains and losses. These gains and losses can be through evaporative cooling (wet bulb temperature), radiant heating (globe temperature), and convection of sensible heat (dry bulb temperature).

Findings from the Study

Strong geological patterns were connected to those who suffered from EHS. Many fatal heat strokes occur under unusual environmental conditions, but not always. For example, athletes who are accustomed to training in New England may not perform the same in the southern zone, such as Tennessee, due to differentiating environmental conditions.

Overall, maximum exposure to WBGT was typically greater in the south. There is also a similar correlation between these environmental conditions with military use. Soldiers from the northern United States had 1.69 times heat-related illnesses while serving in intense heat conditions, vs. soldiers who were more acclimated to the heat.

Since the study, several major national organizations in the US have adopted WBGT regional guidelines to keep athletes safe. These organizations include USTA (tennis), MLS (soccer) and the NCAA.

Today, WBGT regional guidelines are also used beyond athletic use for heat stress safety. It's also used by the US military, the ACSM, and the Occupational Safety and Health Administration.

Monitoring Heat Stress Conditions with Kestrel

Kestrel Weather Meters are the most accurate devices on the market for monitoring heat stress. No matter if you're a novice or professional athlete, being aware of the environment around you can help save a life. The Kestrel 5400 Heat Stress Tracker has regional guidelines pre-loaded in the unit – it's easy and convenient to simply select your designated zone and receive alerts on a mobile device if conditions become dangerous. With data logging capabilities, documenting conditions is a breeze – you can share or export records right from the free Kestrel LiNK app. Consider our top-of-the-line weather meters for ensuring heat stress safety.

About author

Monica Devlin